The UPC is participating in the PaperChain European project, an initiative designed to develop a circular economy model in which waste generated by the paper industry is recovered and used as raw materials in the construction, mining, and chemical sectors, among others. The first tests in Spain are being carried out in Zaragoza province, where the viability of using ashes as alternative binders for roads is being assessed.

ThePaperChain project, coordinated by Acciona, has 20 participating members in five European countries and includes large-scale tests in various operating environments: the construction sector in Spain (layers of stabilised soil in roads), Portugal (asphalts and cements), Slovenia (composite materials for slope stabilisation), and Sweden in the chemical sector (bioethanol for secondary chemical products) and the mining sector (sealing layers for mining spoil). With a budget of 7.8 million euros, the project is funded by the EU research and innovation programme Horizon 2020.

A team of researchers from the UPC Construction Materials and Roads (MATCAR) research group, comprised of Rodrigo Miró, Adriana Martínez, Félix-Edmundo Pérez, and Marilda Barra, is taking part in the project. The team is working on improving and stabilising the level ground that supports a road surface. The binder that is normally used to strengthen resistance to traffic is cement or lime. In this case, ashes from the paper industry are used instead. Ash binders considerably reduce the carbon footprint in the construction of roads, as cement and calcium produce high CO2 emissions.

The research team is also responsible for characterising the materials (soils and ashes) and assessing the mechanical properties of their resulting combination, to define the working formula for use in the construction stages. This research includes a durability study using tests that simulate long-term climate effects.

Practical cases in Zaragoza To assess the feasibility of using ashes, two test stretches of road in Zaragoza province are been monitored using an auscultation system. The first test is being completed this October in Ejea de los Caballeros and consists in the stabilisation of a kilometre-long stretch of unpaved road in the surroundings of a periurban park. The second test, which is taking place in Villamayor de Gállego, consists of refurbishing a kilometre-long stretch of road surface and adding a layer of stabilised soil.

The advantages of adding ash to these soils are the near elimination of swelling, that is, the increase in volume experienced by some soils when their water content increases, and increased bearing capacity, i.e., the capacity of the ground to support loads. These two advantages will lead to considerable savings in road maintenance. This area of Zaragoza has an extensive network of rural roads and intensive agricultural and livestock activity, which means that roads are frequently used by heavy machinery.